Still doesn't add up. As accurate as your analysis was, let me add one more facet, it was also aimed at ensuring that we could mobilize and fight a geographically limited high intensity conflict which was not initiated by us (eg. Kargil) in a more plausible manner, without requiring a long lead time for building up the required force levels in the AO (as in be able to get there quicker, respond faster..etc.).
But as I said, it still does not explain the tac nukes. Tac nukes come into play only when you are met with a true over-match, why would anyone use tac nukes or project using them short of such a scenario given the casualties one would incur when using it over one's own territory? I mean forget the winds, the reason I picked the Marala headworks is that an ERW would poison much of Punjab's water source irrespective of where the wind subsequently blows the fall-out towards. Such a price is only acceptable if no other means of conventionally defending the territory or uprooting the enemy remain. Now that is what bothers me, for the PA too has been working on greater mobility and being in fighting shape, it could most definitely meet a limited offensive face to face so where does the need for tac nukes arise?
Deterrence. The idea that they exist and that they might be used.
As I mentioned earlier, the Marala headworks may not be the best avenue for a push.. since they are too well defended and will extract too many casualties in an attempt to use them as the point of attack . Capturing them may be a more realistic objective as a bargaining chip. Even then, holding them would be difficult.. as the location is a stone's throw away from the Major Reinforcement Base at Kharian.
I would look further north , where there is infrastructure parallel to the border to carry out pincer movements and allows the IAF cover for strikes as well.